Nikon D90 Viewfinder

Nikon D90 Viewfinder

As with most DSLRs, the Nikon D90 has an optical viewfinder that lets you view your subject through the lens. Following a popular trend though, it also offers a Live View mode, in which the mirror flips up and the main image sensor continuously captures a live image of the subject, displaying it on the rear-panel LCD screen. (More on this in a bit.)

Apart from its Live View option, the optical viewfinder is basically the same as that on the previous D80 model. A diopter adjustment dial adjusts the focusing of the viewfinder optics to accommodate eyeglass wearers, and the viewfinder also has quite a high eyepoint (meaning you can see the full frame with your eye a good distance from the rear objective). The 19.5mm eyepoint is fairly good, but I personally (Dave speaking here) do still did still find myself pressing my eyeglass lens against the rubber eyecup in order to see the full frame clearly. The -2.0 to +1.0 diopter adjustment range of the viewfinder optics isn't nearly enough to accommodate my own very nearsighted (20:180) vision, but is more than ample to handle my "computer glasses", which are set to provide good focus for my eyes at a distance of about 18-24 inches. (Frankly, people as nearsighted as me are unlikely to ever walk around without some degree of vision correction, so the dioptric adjustment range of the D80 should be more than sufficient for most users.)

The graphic and table below shows what information is displayed in D90's viewfinder.

While the D90's viewfinder optics match those of the D80 pretty closely, one notable change is that the AF points are no longer etched on the viewfinder screen, but rather appear courtesy of an overlay LCD. This is nice because when the AF points aren't being displayed, there's nothing to obscure your view of the subject. The D90's viewfinder screen is similar to that on the recently announced D700.

One big plus about the D90's viewfinder is its size: It's basically the same viewfinder as used on the D200/300, and is very noticeably larger than the viewfinders on other Nikon consumer SLRs. While I dislike having to press my eyeglasses up against the eyecup, all of us at IR really like having a larger viewfinder image to look at.

Here's another, more subtle point about the Nikon D90's viewfinder: It uses a true pentaprism, rather than the pentamirror arrangement that's all but universal in consumer-level SLRs. The reason this is important is that pentaprisms are much brighter. This is because a convenient trick of optics lets prisms reflect 100% of the light passing through them, so no light is lost as it bounces around inside and then back out the eyepiece. Even the best mirrors typically pass only 96-98% of the light falling on them. In a pentamirror, with three reflections required to bounce the light into your eye, this means that anywhere from 6 to 12% of the light is lost, making for a noticeably darker viewfinder image.

When it comes to accuracy, the D90's viewfinder is rated to show 96% of the final image area, about as good as you'll get without going to a considerably more expensive SLR.